Former graduate student here. The most important thing to remember is that every paper has a main point, and everything in it is reinforcing that main point. Figure out what the point is. The whole story is in the figures.

Start with the title. Then look at each of the figures carefully. Figure out the limits of the paper from the methods. Certain methods can only give certain types of results. Again, look at the figures. The figures tell the whole story and are worth way more than the text. What is the story the figures tell?

Ignore the rest of the text. If you must read something, read the text of the results and look at the supplement. If you have a lot of spare time, skim the citations and identify the couple of sentences in the discussion that express the author’s methodological regrets. Under no circumstances should you read an introduction.